Because the system has been told to use less power, so it refreshes at half the rate, therefore you eyes see flicker! Turn it OFF! Your eyes will thank you later on in life! If you can't afford the normal power bill, don't turn it on!
If this is some thing that is wrong, take it back to the store you bought it from! Better yet, go back and ask them what the issue is, as you are not satisfied and you need an explanation of what is the matter with your TV!